Gelatine silver halide emulsion layer containing a dihydroxy diphenyl tanning developing agent



Apnl 8, 1952 c, YACKEL 2,592,368

GELATINE SILVER HALIDE EMULSION LAYER CONTAINING A DIHYDROXY DIPHENYL TANNING DEVELOPING AGENT Filed Nov. 4, 1947 FIG l /6/L VER HAL/DE EMULSION CONTAIN/N6 INSOLUBLE TANN/NG DEVELOPING AGE/V7 J0 TRA C/NG' C'LOTH 67L VER lMAGE IN TANNED COLLOID J3 A EMULSION DEVELOPED 10 ALKAL/ SOLUTION UNTANNED EMULSION WASHED OFF 10 EDWARD C YACKEL INVENTOR W.M BY fiaw ewf ATTORNEYS Patented Apr. 8, 1952 OFFICE GELATINE SILVER HALIDE EMULSION LAYER CONTAINING A, DIHYDROXY DIPHENYL T A N N I N G DEVELOPING AGENT Edward C. Yackel, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application November 4, 1947, Serial No. 783,912

4 Claims.

This invention relates to light-sensitive photographic materials and particularly to improved types of sensitized materials suitable for making images in tanned colloid vehicle.

In the sensitized photographic tracing cloth at present available a silver halide emulsion is coated on a subbed tracing cloth which has generally been waterproofed. This material sometimes has the. disadvantage that the processed cloth shows a bad tendency to curl which interferes with its every-day use and with filing of the finished drawing. Another disadvantage is that erasures and corrections on the processed sheet are diflicult because of the presence of gelatin. In another type of tracing cloth in which bichromated'gelatin is used the photographic speed of the material is extremely low and the unexposed or unprocessed material has poor keeping properties.

I have found that it is possible to incorporate a. tanning developing agent into a photographic emulsion on a support such as tracing cloth and after exposure and development to form relief images by washing the unexposed emulsion away with water. veloping agent such as pyrocatechol or hydro- .quinone is used, because of solubility, vapor pressure, etc., the developing agent does not remain in the emulsion layer during long periods of keeping. Instead, it wanders throughout the gelatin and waterproofing layer of a material such as tracing cloth and from one piece of material to another when the two are in close contact. This Wandering of the developing agent results in undesirable stain, poor developability, etc. ever, if a substantially water-insoluble tanning developing agent is used inthe emulsion layer the objections to a more soluble type of developing agent are overcome. In addition, when emulsion layers are compounded with the substantially water-insoluble tanning developing agents according to my invention such emulsion layersare eminently suitable for use in a process of the type described and claimed, in Yutzy and Yackel U. S. patent application, Serial No. 783,914 filed concurrently herewith.

It is therefore an object of the present invention to provide light-sensitive photographic emulsion layers containing substantially water-insoluble tanning developing agents. A further object is to provide a sensitized tracing cloth having improved properties. Other objects will appear from the following description of my invention.

These objects are accomplished in part by incorporating a substantially water-insoluble tan- However, if a soluble tanning de- Howning developing agent-in a light-sensitive photographic emulsion layer, and further, by coating such an emulsion layer ona tracing cloth or other support and after exposure and development in analkali solution, treating the element with warm water'to wash away the undevelopedsilver. halide with its vehicle. This leaves-a tanned colloid relief image on the tracing cloth or other support and providesan image carrying materia1 which is substantially free from curl and on which erasures or corrections can be madeandwhich has good keeping properties.

In the accompanying drawings, the three figures are enlarged cross-sectional views of the tracing cloth at various stages in my process.

According to my invention a light-sensitive silver'salt emulsion layer containing a substantially water insoluble tanning developing agent is prepared. According to my method of using such an emulsion layer it is coated on a support such as'tracing cloth, a cellulose ester film baseglass, or paper. Fine-grain gelatino-silver bromide emulsions are preferably used but silverchloride or other silver halide emulsions may be used in gelatin or other vehicles such as polyvinyl alcohol, which can be differentially tanned with tanning developing agents.

The developing agent may be any substantially water-insoluble developing agent which tans the gelatin or other carrier, for the silver halide, upon development in an alkaline solution. Examples of tanning developing agents specially useful because of their non-wandering characteristics, high rate of development, high tanning efliciency, and solubility in the preferred range, are those having a solubility of from about .005 to 1.0 gram per hundredcc. of a phosphate citric acid buffer solution of pH 5.0 prepared from a 1.5 per cent solution of sodium dihydrogenphosphate and sufficient citric acid to bring the pH to 5.0. The preferred developing agent has the solubility of from about .01 to 0.2 gram per hundred cc. of buffer solution. Developing agents following within the above classification arepfor example, 3,4-dihydroxy diphenyl; 2,5-dihydroxy diphenyl; 2,3-dihydroxy diphenyl; and 5,6,'7,8-tetrahydro napthohydroquinone. Compounds like 2-hydroxy-5-amino-diphenyl or 3,4-diaminodipheny1 are not especially useful because of their poor stability characteristics or failure to differentially tan the emulsion vehicle.

Here and in the appended claims wherein it is stated that the developing agents are substantially water-insoluble this is defined as meaning tanning developing agents having solubility within the above range of buffer solution.

Here and in the appended claims wherein it is stated that the emulsion vehicle is substantially unhardened this is defined as meaning not harder than would be the case with gelatin containing 0.25 ounce of formaldehyde (40 per cent solution diluted 1 to 3 with water) per pound, when freshly coated, or 0.1 ounce of the solution per pound for a sample aged three to six months. Emulsion layers appreciably harder are not very satisfactory for use in my process or that of the above oopending application. 7

In general, when utilizing the usual type of photographic gelatin useful results are obtained without addition of hardener to the emulsion. In case the gelatin in use has poor physical properties then a small amount of hardener such as formaldehyde may be used.

The emulsion layer prepared as above is exposed in the usual manner under a line drawing and is "developed by immersion in an aqueous solution of an alkali such as sodium or potassium carbonate, an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide, or an amine. The addition to the alkaline solution, of other materials, is also helpful in obtaining a satisfactory relief image. For example, the addition of sodium hydroxide to a sodium carbonate solution improves the sensitometric characteristics of the material as well as the relief properties. The addition of reducing agents such as ascorbic acid, hydrazine hydrochloride, sodium sulfite, in small quantities, sodium bicarbonate and urea, are also advantageous.

After development of the exposed material in the alkaline solution the element is washed with warm water to remove the unexposed and undeveloped colloid and silver halide and then dried. By warm water I mean water at a temperature of about 90 F. to 100 F. or higher My invention will be further understood by reference to the following examples which are illustrative only.

Example I while stirring the latter over a period of about 10 minutes; Solution B preferably not being allowed to run in faster than C. Thereafter, 150 grams of gelatin in 1500 cc. of water at 40 C. are added. The emulsion is then adjusted to pH of 5.0. If desired, the emulsion may then be chilled, set, and washed in the usual manner. It is then remelted and 25 grams of 3,4-dihydroxy diphenyl dissolved in 250 cc. of methyl alcohol is slowly added to the above emulsion with stirring. As a result the developing agent becomes dispersed in the emulsion in minute crystals. Preparatory to coating an emulsion layer, in case a gelatin having poor physical properties has been used, 2 cc. of 10% formaldehyde may be added and this composition is coated on a prepared tracing cloth support over an area of about 500 square feet and dried. The

dried product is exposed to a suitable negative and developed in a 4 percent sodium carbonate solution. The developed element is then washed with water at 35 C. to remove the unexposed, undeveloped and untanned emulsion, is then rinsed and dried. A positive relief image in gelatin is thus obtained with no gelatin remaining in the unexposed area. Erasures and redrawing of lines were as satisfactory on the print as on the uncoated tracing cloth. Curl was greatly diminished and was approximately equivalent to that of the uncoated tracing cloth, after having been processed through the same baths.

Example II Another emulsion suitable for use in my invention is made from the following solutions-(A) 25 grams gelatin in 1 liter water at 40 C.; (B) grams silver nitrate dissolved in 500 cc. water at 20 C.; (C) '72 grams potassium bromide in 500 cc. water at 20 C. Solutions B and C are simultaneously run into Solution A with stirring and afterwards a solution of 200 grams gelatin in 2 liter water at 40 C. is added. A suitable surface-active agent may then be added and the pH adjusted to 5.0. Thereafter a solution of 25 grams of 4-phenyl catechol in 250 cc. of methyl alcohol is added with stirring. Preparatory to coating the emulsion on a support as tracing cloth, a small quantity of hardener may be added as in Example I following which the emulsion is coated over an area of about 300 square feet.

The concentration of developing agent in the emulsion is dependent in part on the result desired but can be of the order of 350 grams per kg. of silver nitrate, converted to silver halide. used in making the emulsion, to obtain good density, or about 250 grams per kg. of silver nitrate to obtain adequate density and an emulsion having optimum keeping properties.

In the accompanying drawings, I have shown a typical tracing cloth at various stages in my process. As shown in Fig. 1, a support ill of sized tracing cloth is coated with a gelatinosilver halide emulsion II containing a substantially water insoluble tanning developing agent. This material is exposed and developed by immersion in an alkaline solution to form images of silver and hardened gelatin as shown at I 2 in Fig. 2. The remaining unhardened gelatin and silver halide I3 in Fig. 2 is then washed off by treatment of the tracing cloth with warm water to leave images ll of hardened gelatin on the support III as shown in Fig. 3.

I am aware that the incorporation of organic developing agents in emulsions to form self-developing emulsions is well known and that the use of hardening developers in solution to form hardened gelatin images for use in the production of relief images, is also known. However, I am not aware that substantially waterinsoluble hardening developing agents of the type specified above have been incorporated in light-sensitive silver salt emulsions and the resulting emulsions used to form tanned images.

My invention having been described, I would have it understood that the disclosure herein is by way of example and included in the invention are all modifications and equivalents falling within the scope of the appended claims.

What I claim is:

l. A photographic emulsion layer comprising a substantially unhardened gelatin vehicle and dispersed in said vehicle a silver halide and a tanning developing agent of the class consisting of 2,3-dihydroxy diphenyl, 2,5-dihydroxy diphenyl, and 3,4-dihydroxy diphenyl.

- 5 2. A photographic emulsion layer comprising Number gelatin, silver halide, and 2,3-dihydroxy diphenyl. 1,535,700 3. A photographic emulsion layer comprising 1,709,569 gelatin, silver halide, and 2,5-dihydroxy diphenyl. 1,812,981 4. A photographic emulsion layer comprising 5 2,039,730 gelatin, silver halide, and 3,4-dihydroxy diphenyl. 2,090,484

EDWARD C. YACKEL. 2,126,899

2,315,966 REFERENCES CITED 2,334 215 The following references are of record in the 10 213501124 file of this patent: 2,409,959

UNITED STATES PATENTS Number Name Date Number 742,405 Eichengrun Oct. 27, 1903 23,251 1,102,028 Fischer June 30, 1914 581,479 1,472,048 Christensen Oct. 30, 1923 6 Name Date Troland Apr. 25, 1925 Procoudine-Gorsky Apr. 16, 1929 Procoudine-Gorsky July 7, 1931 Mannes et a1. May 5, 1936 Ostromislensky Aug. 17, 1937 Lieber- Aug. 16, 1938 Knott Apr. 6, 1943 Nadeau et a1. Nov. 16, 1943 Nadeau et a1 May 30, 1944 Ryan Oct. 22, 1946 FOREIGN PATENTS Country Date Great Britain Dec. 16, 1892 Great Britain Oct. 14, 1946 

1. A PHOTOGRAPHIC EMULSION LAYER COMPRISING A SUBSTANTIALLY UNHARDENED GELATIN VEHICLE AND DISPERSED IN SAID VEHICLE A SILVER HALIDE AND A TANNING DEVELOPING AGENT OF THE CLASS CONSISTING OF 2,3-DIHYDROXY DIPHENYL, 2,5-DIHYDROXY DIPHENYL, AND 3,4-DIHYDROXY DIPHENYL. 